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<div><font face="Arial" color="#000000">Seminar on<br>
<b>Modern Optics and Spectroscopy<br>
<br>
<br>
</b></font><font face="Times New Roman"
color="#000000"> </font><font face="Arial"
color="#000000"><b>János Hebling</b>, MIT<br>
<br>
<i><b>Generation and application of high field THz pulses<br>
<br>
</b></i>April 17, 2007</font><br>
<font face="Arial" color="#000000"></font></div>
<div><font face="Arial" color="#000000">12:00 - 1:00 p.m.</font></div>
<div><font face="Arial" color="#000000">Grier Room 34-401</font></div>
<div><font face="Times"
color="#000000"><x-tab>
</x-tab><br>
<br>
</font><font face="Times New Roman" color="#000000">During the last
two decades the fast development of time domain THz spectroscopy
(TDTS) created a renaissance of this field and related applications of
near-single-cycle THz pulses. Although the majority of TDTS
work has been done by THz pulses having ralatively small energy on the
fJ - pJ range there exists a strong and yet unmet need for high energy
ultrashort THz pulses for applications in imaging, security control
and nonlinear THz spectroscopy. For this purpose in the last few years
we developed an efficient THz pulse generation technique based on
optical rectification of ultrashort near-IR pump pulses in lithium
niobate (LN) crystal. This method achieves matching of the effective
pump pulse group velocity to the phase velocity of the THz pulses by
so called tilted-pulse-front-excitation. After describing the
principle, the set-up and the results achieved by this technique a few
of our preliminary nonlinear THz optics and spectroscopy results will
be presented. The possible combination of the
tilted-pulse-front-excitation with shaped pump pulses will also be
sketched. The latter was earlier used at MIT for generation, coherent
addition and control of phonon-polaritons (mixture of THz
electromagnetic field and lattice vibration) in ferroelectrics (i.e.
LN). The combination of the two techniques will enable the generation
of high energy THz pulses for (quantum) control experiments with
practically arbitrary pulse shape if the spectrum is on the 0.1 - 2
THz range and the pulse duration shorter than 10 ps</font></div>
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